| 摘要 |
A tone detector, e.g. dial tone, for an automatic telephone answering system comprises a signal detector responsive to voice and steady tone signals for providing an indication of the status of an incoming signal on a telephone line, and a processor for monitoring line signal status to determine the presence of dial tone and to automatically disconnect the system from the telephone line. The determination of dial tone is made based upon the continuous existence, over a predetermined time interval, of an incoming line signal status representative of a steady tone signal. When the automatic telephone answering system includes a message recording system and remote access message playback a processor actuated circuitry for inserting a blank interval in an incoming tone signal prior to being recorded is provided. This prevents replayed tones from disconnecting the system from the telephone line. |
